1. Field of the Invention
The present invention relates to a novel phosphine transition metal complex having a ferrocene skeleton, a process for making the complex, and an anti-cancer agent containing the complex.
2. Description of the Related Art
It is widely known that cisplatin has excellent anti-tumor activity against cancerous cells. Cisplatin is currently the mainstream of anti-cancer agents. It is also known that some types of phosphine transition metal complexes including 1,2-bis(diphenylphosphino)ethane have anti-cancer activity comparable to that of cisplatin (e.g., refer to PCT Japanese Translation Patent Publication No. 10-509957 ('957 document) and Japanese Unexamined Patent Application Publication No. 61-10594 ('594 document)).
The aforementioned patent documents propose a phosphine transition metal complex represented by general formula (6) below.
'957 document provides a phosphine transition metal complex represented by general formula (6) wherein R1 to R8 may be the same or different and each represent a group selected from phenyl, substituted phenyl, 4-pyridyl, 3-pyridyl, and 2-pyridyl, A1 represents —(CH2)n— or cis-CH═CH—, M1 represents gold, silver, or copper; and B1 represents a halogen atom such as chlorine. '594 document provides a phosphine transition metal complex represented by general formula (6) wherein R1 to R8 represent the same group selected from a phenyl group, an ethyl group, or a mono-substituted phenyl group, A1 represents —(CH2)n— or cis-CH═CH—, M1 represents gold, silver, or copper; and B1 represents a halogen atom such as chlorine, and a phosphine transition metal complex wherein B1 represents halogen, PF6, or NO3.
In general, it is known that anti-cancer activity and anti-cancer spectrum of a compound depend upon the chemical structure of the compound and that the efficacy of the compound differs from person to person. For example, even taxol, which is considered as the best anti-cancer agent, has an efficacy of only about 30%. Development of various novel anti-cancer agents with different chemical structures is desired.
The present inventors have conducted extensive investigations on novel phosphine transition metal complexes having anti-cancer activity and found that a phosphine transition metal complex produced by reacting a phosphine derivative having a particular structure with a transition metal salt of gold, copper, platinum, or silver has excellent anti-cancer activity. Thus, the present inventors have made the present invention on the basis of such findings.